Cardano vs Ethereum
Cardano (ADA) was created after Bitcoin and Ethereum and thus could learn from their mistakes and build on their strengths. Its founder and CEO Charles Hoskinson call it a third-generation cryptocurrency, meaning that it already has some of the features that earlier cryptos are struggling to implement.
Cardano uses a modification of the Proof-of-Stake consensus algorithm called Oroboros, which makes the network extremely scalable. At the same time, Ethereum is only planning to transit from the clunky Proof-of-Work to the faster, more energy-efficient Proof-of-Stake. In this sense, ADA is already far ahead.
Yet another factor that is in play in the Ethereum vs Cardano race is team cohesion. ADA is a commercial project, and all the coders and researchers on the team are paid a salary. The Ethereum development community is a mishmash of teams, mostly unpaid, who argue with each other and propose competing ideas.